Effective Lagrangian for a Technicolor Model without Exact Custodial Symmetry

Effective Lagrangian including technimesons is constructed for a realistic one-family Technicolor model without exact custodial symmetry. Tree level contribution to oblique correction parameters $S$ and $U$ due to spin 1 technimesons are computed with the effective Lagrangian. An isospin breaking term which is associated with technilepton vector mesons gives a negative contribution to the electroweak radiative correction parameter $S$ due to mixing between $I=0$ and $I=1$ vector mesons. $U$ receives non-zero contribution due to exotic left-handed charged vector mesons and its sign can be both negative and positive.Comment: 30 pages plus 1 table and 4 figures (7 postscript files append.), Latex, (HUPD-9406

Primordial Lepton Family Asymmtries in Seesaw Model

In leptogenesis scenario, the decays of heavy Majorana neutrinos generate lepton family asymmetries, $Y_e, Y_{\mu}$ and $Y_{\tau}$. They are sensitive to CP violating phases in seesaw models. The time evolution of the lepton family asymmetries are derived by solving Boltzmann equations. By taking a minimal seesaw model, we show how each family asymmetry varies with a CP violating phase. For instance, we find the case that the lepton asymmetry is dominated by $Y_{\mu}$ or $Y_{\tau}$ depending on the choice of the CP violating phase. We also find the case that the signs of lepton family asymmetries $Y_{\mu}$ and $Y_{\tau}$ are opposite each other. Their absolute values can be larger than the total lepton asymmetry and the baryon asymmetry may result from the cancellation of the lepton family asymmetries.Comment: 26 pages, 8 figures, ptp.styl

Neutrino mixing in Seesaw model

We study the neutrino mixing matrix (the MNS matrix) in the seesaw model. By assuming a large mass hierarchy for the heavy right-handed Majorana mass, we show that, in the diagonal Majorana base, the MNS matrix is determined by a unitary matrix, $S$, which transforms the neutrino Yukawa matrix, $y_{\nu}$, into a triangular form, $y_{\triangle}$. The mixing matrix of light leptons is $V_{KM} S^{\prime *}$, where $V_{KM} \equiv {V_{Le}}^{\dagger} V_{L \nu}$ %$V_{Le}$ and $V_{L\nu}$ diagonalize %the Yukawa matrices of charged leptons, %$y_e y_e^{\dagger}$, and neutrinos, $y_{\nu} y_{\nu}^{\dagger}$, %respectively, and $S^{\prime *} \equiv {V_{L\nu}}^{\dagger} S^*$. Large mixing may occur without fine tuning of the matrix elements of $y_{\triangle}$ even if the usual KM-like matrix $V_{KM}$ is given by $V_{KM} =1$. This large mixing naturally may satisfy the experimental lower bound of the mixing implied by the atmospheric neutrino oscillation.Comment: 14 pages, 4 figures, PTPTe

Numerical study on the correlation between CP violation in neutrino oscillations and baryogenesis

We numerically study the correlation between CP violation in the neutrino oscillations and baryogenesis in the seesaw model. In this study we get the heavy Majorana neutrino masses and lepton number asymmetries from their decays by fitting the data of neutrino oscillations and by working on some hypothesis of the Dirac-Yukawa term for neutrinos.Comment: 3 pages, 2 figures, Latex, presented at KEKTC5(Nov. 2001), to be published in Nucl. Phys. Proc. Supp

Low scale Seesaw model and Lepton Flavor Violating Rare B Decays

We study lepton flavor number violating rare B decays, $b \to s l_h^{\pm} l_l^{\mp}$, in a seesaw model with low scale singlet Majorana neutrinos motivated by the resonant leptogenesis scenario. The branching ratios of inclusive decays $b \to s l_h^{\pm} \bar{l_l}^{\mp}$ with two almost degenerate singlet neutrinos at TeV scale are investigated in detail. We find that there exists a class of seesaw model in which the branching fractions of $b \to s \tau \mu$ and $\tau \to \mu \gamma$ can be as large as $10^{-10}$ and $10^{-9}$ within the reach of Super B factories, respectively, without being in conflict with neutrino mixings and mass squared difference of neutrinos from neutrino data, invisible decay width of $Z$ and the present limit of $Br(\mu \to e \gamma)$.Comment: 19 pages, 6 figure

Cosmological Family Asymmetry and CP violation

We discuss how the cosmological baryon asymmetry can be achieved by the lepton family asymmetries of heavy Majorana neutrino decays and they are related to CP violation in neutrino oscillation, in the minimal seesaw model with two heavy Majorana neutrinos. We derive the most general formula for CP violation in neutrino oscillation in terms of the heavy Majorana masses and Yukawa mass term. It is shown that the formula is very useful to classify several models in which $e-$, $\mu-$ and $\tau-$leptogenesis can be separately realized and to see how they are connected with low energy CP violaton. To make the models predictive, we take texture with two zeros in the Dirac neutrino Yukawa matrix. In particular, we find some interesting cases in which CP violation in neutrino oscillation can happen while lepton family asymmetries do not exist at all. On the contrary, we can find $e-$, $\mu-$ and $\tau-$leptogenesis scenarios in which the cosmological CP violation and low energy CP violation measurable via neutrino oscillations are very closely related to each other. By determining the allowed ranges of the parameters in the models, we predict the sizes of CP violation in neutrino oscillation and $|V_{e3}^{MNS}|$. Finally, the leptonic unitarity triangles are reconstructed.Comment: 22 pages, 9 figures A figure caption correcte